SPHiEEECHIXUS. 



159 



Spbserechinus brevispinosus, Desor, Syn. Ech.foss. (1858) p. 134. 

 Echinus esculentus, de Bl. Diet. Sci. Nat. xxxvii. (1825) p. 86. 

 Sphserechinus esculentus, Bronn, Kl. u. Ordn. ii. (1860) pi. xxxvii. 



figs. 1-3 & 5-14, pi. xxxix. figs. 6 & 8. 

 Echinus equituberculatus, de BL Diet. Sci. Nat. xxxvii. (1825) p. 86 



(not p. 76). 

 Echinus asquituberculatus, Desmoulins, Syn. Echin. (1837) p. 280. 

 Echinus subglobiformis, de. Bl. Diet. Set. Xat. xxxvii. (182-5) p. 89 ; 



Desmoulins, Syn. Ech. (1837) p. 282. 

 Echinus dubius, de Bl. op. cit. p. 87 ; Desm. op. cit. p. 280. 

 Echinus ( Toxopneustes) albidus, Ay. §Des. Ann. Sci. Nat. vi. (1846) 



p. 367. 



Test may attain some size. Primary spines short, very numerous, 

 rather blunt, white, purple, purple tipped with white, pink, red or 

 brown ; secondary spines inconspicuous ; pedicellariae globiferaa 

 enormous. 



Test hemispherical or slightly conical, not often depressed ; stout, 

 thickly covered with primary tubercles. Small peristome, compact 

 ealycinal area, rather large periproct. 



In a typical specimen there are rather more than thirty plates in 

 each interambulacral series, and those at the ambitus are about 

 three times as wide as deep ; they there bear six primary tubercles 

 each, and this number only slowly decreases as either pole of the 

 test is reached ; the primary tubercles are not very prominent, but 

 their large number gives a special facies to the test ; scattered 

 around and between them are small miliaries. The primaries of the 

 ambulacral plates are somewhat smaller than those of the inter- 

 ambulacral ; there are, at the ambitus, two on either plate, and the 

 inner of these disappears somewhat more rapidly above than below 

 the ambitus, so that a narrow, almost bare space is left near the apex 

 of the test ; near the line of suture one of the secondary tubercles is 

 often rather prominent. The poriferous zones vary somewhat in 

 breadth, the arrangement of the pairs of pores in arcs being in- 

 constant. Each compound pore-plate may carry five or six pairs of 

 pores, and on each there is one rather large tubercle. 



The plates of the ealycinal area form a narrow ring, and even the 

 madreporite is not very prominent : the tuberculation is inconstant ; 

 two of the radials touch the periproct, which is of an elongated 

 oval form. The vent is excentric ; round it are some very small 

 plates, but the rest of the circumanal plates are rather large. 



The test may be of a purplish or pinkish hue : the poriferous zones 

 are generally of a lighter hue than the rest of the test, but appear 

 to be somewhat depressed in consequence of the smaller size of the 

 tubercles on than those to either side of them. 



